--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/concurrentMark.hpp Wed May 13 15:16:06 2015 +0200
@@ -0,0 +1,1227 @@
+/*
+ * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_G1_CONCURRENTMARK_HPP
+#define SHARE_VM_GC_G1_CONCURRENTMARK_HPP
+
+#include "classfile/javaClasses.hpp"
+#include "gc/g1/g1RegionToSpaceMapper.hpp"
+#include "gc/g1/heapRegionSet.hpp"
+#include "gc/shared/gcId.hpp"
+#include "gc/shared/taskqueue.hpp"
+
+class G1CollectedHeap;
+class CMBitMap;
+class CMTask;
+class ConcurrentMark;
+typedef GenericTaskQueue<oop, mtGC> CMTaskQueue;
+typedef GenericTaskQueueSet<CMTaskQueue, mtGC> CMTaskQueueSet;
+
+// Closure used by CM during concurrent reference discovery
+// and reference processing (during remarking) to determine
+// if a particular object is alive. It is primarily used
+// to determine if referents of discovered reference objects
+// are alive. An instance is also embedded into the
+// reference processor as the _is_alive_non_header field
+class G1CMIsAliveClosure: public BoolObjectClosure {
+ G1CollectedHeap* _g1;
+ public:
+ G1CMIsAliveClosure(G1CollectedHeap* g1) : _g1(g1) { }
+
+ bool do_object_b(oop obj);
+};
+
+// A generic CM bit map. This is essentially a wrapper around the BitMap
+// class, with one bit per (1<<_shifter) HeapWords.
+
+class CMBitMapRO VALUE_OBJ_CLASS_SPEC {
+ protected:
+ HeapWord* _bmStartWord; // base address of range covered by map
+ size_t _bmWordSize; // map size (in #HeapWords covered)
+ const int _shifter; // map to char or bit
+ BitMap _bm; // the bit map itself
+
+ public:
+ // constructor
+ CMBitMapRO(int shifter);
+
+ enum { do_yield = true };
+
+ // inquiries
+ HeapWord* startWord() const { return _bmStartWord; }
+ size_t sizeInWords() const { return _bmWordSize; }
+ // the following is one past the last word in space
+ HeapWord* endWord() const { return _bmStartWord + _bmWordSize; }
+
+ // read marks
+
+ bool isMarked(HeapWord* addr) const {
+ assert(_bmStartWord <= addr && addr < (_bmStartWord + _bmWordSize),
+ "outside underlying space?");
+ return _bm.at(heapWordToOffset(addr));
+ }
+
+ // iteration
+ inline bool iterate(BitMapClosure* cl, MemRegion mr);
+ inline bool iterate(BitMapClosure* cl);
+
+ // Return the address corresponding to the next marked bit at or after
+ // "addr", and before "limit", if "limit" is non-NULL. If there is no
+ // such bit, returns "limit" if that is non-NULL, or else "endWord()".
+ HeapWord* getNextMarkedWordAddress(const HeapWord* addr,
+ const HeapWord* limit = NULL) const;
+ // Return the address corresponding to the next unmarked bit at or after
+ // "addr", and before "limit", if "limit" is non-NULL. If there is no
+ // such bit, returns "limit" if that is non-NULL, or else "endWord()".
+ HeapWord* getNextUnmarkedWordAddress(const HeapWord* addr,
+ const HeapWord* limit = NULL) const;
+
+ // conversion utilities
+ HeapWord* offsetToHeapWord(size_t offset) const {
+ return _bmStartWord + (offset << _shifter);
+ }
+ size_t heapWordToOffset(const HeapWord* addr) const {
+ return pointer_delta(addr, _bmStartWord) >> _shifter;
+ }
+ int heapWordDiffToOffsetDiff(size_t diff) const;
+
+ // The argument addr should be the start address of a valid object
+ HeapWord* nextObject(HeapWord* addr) {
+ oop obj = (oop) addr;
+ HeapWord* res = addr + obj->size();
+ assert(offsetToHeapWord(heapWordToOffset(res)) == res, "sanity");
+ return res;
+ }
+
+ void print_on_error(outputStream* st, const char* prefix) const;
+
+ // debugging
+ NOT_PRODUCT(bool covers(MemRegion rs) const;)
+};
+
+class CMBitMapMappingChangedListener : public G1MappingChangedListener {
+ private:
+ CMBitMap* _bm;
+ public:
+ CMBitMapMappingChangedListener() : _bm(NULL) {}
+
+ void set_bitmap(CMBitMap* bm) { _bm = bm; }
+
+ virtual void on_commit(uint start_idx, size_t num_regions, bool zero_filled);
+};
+
+class CMBitMap : public CMBitMapRO {
+ private:
+ CMBitMapMappingChangedListener _listener;
+
+ public:
+ static size_t compute_size(size_t heap_size);
+ // Returns the amount of bytes on the heap between two marks in the bitmap.
+ static size_t mark_distance();
+ // Returns how many bytes (or bits) of the heap a single byte (or bit) of the
+ // mark bitmap corresponds to. This is the same as the mark distance above.
+ static size_t heap_map_factor() {
+ return mark_distance();
+ }
+
+ CMBitMap() : CMBitMapRO(LogMinObjAlignment), _listener() { _listener.set_bitmap(this); }
+
+ // Initializes the underlying BitMap to cover the given area.
+ void initialize(MemRegion heap, G1RegionToSpaceMapper* storage);
+
+ // Write marks.
+ inline void mark(HeapWord* addr);
+ inline void clear(HeapWord* addr);
+ inline bool parMark(HeapWord* addr);
+ inline bool parClear(HeapWord* addr);
+
+ void markRange(MemRegion mr);
+ void clearRange(MemRegion mr);
+
+ // Starting at the bit corresponding to "addr" (inclusive), find the next
+ // "1" bit, if any. This bit starts some run of consecutive "1"'s; find
+ // the end of this run (stopping at "end_addr"). Return the MemRegion
+ // covering from the start of the region corresponding to the first bit
+ // of the run to the end of the region corresponding to the last bit of
+ // the run. If there is no "1" bit at or after "addr", return an empty
+ // MemRegion.
+ MemRegion getAndClearMarkedRegion(HeapWord* addr, HeapWord* end_addr);
+
+ // Clear the whole mark bitmap.
+ void clearAll();
+};
+
+// Represents a marking stack used by ConcurrentMarking in the G1 collector.
+class CMMarkStack VALUE_OBJ_CLASS_SPEC {
+ VirtualSpace _virtual_space; // Underlying backing store for actual stack
+ ConcurrentMark* _cm;
+ oop* _base; // bottom of stack
+ jint _index; // one more than last occupied index
+ jint _capacity; // max #elements
+ jint _saved_index; // value of _index saved at start of GC
+
+ bool _overflow;
+ bool _should_expand;
+ DEBUG_ONLY(bool _drain_in_progress;)
+ DEBUG_ONLY(bool _drain_in_progress_yields;)
+
+ oop pop() {
+ if (!isEmpty()) {
+ return _base[--_index] ;
+ }
+ return NULL;
+ }
+
+ public:
+ CMMarkStack(ConcurrentMark* cm);
+ ~CMMarkStack();
+
+ bool allocate(size_t capacity);
+
+ // Pushes the first "n" elements of "ptr_arr" on the stack.
+ // Locking impl: concurrency is allowed only with
+ // "par_push_arr" and/or "par_pop_arr" operations, which use the same
+ // locking strategy.
+ void par_push_arr(oop* ptr_arr, int n);
+
+ // If returns false, the array was empty. Otherwise, removes up to "max"
+ // elements from the stack, and transfers them to "ptr_arr" in an
+ // unspecified order. The actual number transferred is given in "n" ("n
+ // == 0" is deliberately redundant with the return value.) Locking impl:
+ // concurrency is allowed only with "par_push_arr" and/or "par_pop_arr"
+ // operations, which use the same locking strategy.
+ bool par_pop_arr(oop* ptr_arr, int max, int* n);
+
+ // Drain the mark stack, applying the given closure to all fields of
+ // objects on the stack. (That is, continue until the stack is empty,
+ // even if closure applications add entries to the stack.) The "bm"
+ // argument, if non-null, may be used to verify that only marked objects
+ // are on the mark stack. If "yield_after" is "true", then the
+ // concurrent marker performing the drain offers to yield after
+ // processing each object. If a yield occurs, stops the drain operation
+ // and returns false. Otherwise, returns true.
+ template<class OopClosureClass>
+ bool drain(OopClosureClass* cl, CMBitMap* bm, bool yield_after = false);
+
+ bool isEmpty() { return _index == 0; }
+ int maxElems() { return _capacity; }
+
+ bool overflow() { return _overflow; }
+ void clear_overflow() { _overflow = false; }
+
+ bool should_expand() const { return _should_expand; }
+ void set_should_expand();
+
+ // Expand the stack, typically in response to an overflow condition
+ void expand();
+
+ int size() { return _index; }
+
+ void setEmpty() { _index = 0; clear_overflow(); }
+
+ // Record the current index.
+ void note_start_of_gc();
+
+ // Make sure that we have not added any entries to the stack during GC.
+ void note_end_of_gc();
+
+ // iterate over the oops in the mark stack, up to the bound recorded via
+ // the call above.
+ void oops_do(OopClosure* f);
+};
+
+class ForceOverflowSettings VALUE_OBJ_CLASS_SPEC {
+private:
+#ifndef PRODUCT
+ uintx _num_remaining;
+ bool _force;
+#endif // !defined(PRODUCT)
+
+public:
+ void init() PRODUCT_RETURN;
+ void update() PRODUCT_RETURN;
+ bool should_force() PRODUCT_RETURN_( return false; );
+};
+
+// this will enable a variety of different statistics per GC task
+#define _MARKING_STATS_ 0
+// this will enable the higher verbose levels
+#define _MARKING_VERBOSE_ 0
+
+#if _MARKING_STATS_
+#define statsOnly(statement) \
+do { \
+ statement ; \
+} while (0)
+#else // _MARKING_STATS_
+#define statsOnly(statement) \
+do { \
+} while (0)
+#endif // _MARKING_STATS_
+
+typedef enum {
+ no_verbose = 0, // verbose turned off
+ stats_verbose, // only prints stats at the end of marking
+ low_verbose, // low verbose, mostly per region and per major event
+ medium_verbose, // a bit more detailed than low
+ high_verbose // per object verbose
+} CMVerboseLevel;
+
+class YoungList;
+
+// Root Regions are regions that are not empty at the beginning of a
+// marking cycle and which we might collect during an evacuation pause
+// while the cycle is active. Given that, during evacuation pauses, we
+// do not copy objects that are explicitly marked, what we have to do
+// for the root regions is to scan them and mark all objects reachable
+// from them. According to the SATB assumptions, we only need to visit
+// each object once during marking. So, as long as we finish this scan
+// before the next evacuation pause, we can copy the objects from the
+// root regions without having to mark them or do anything else to them.
+//
+// Currently, we only support root region scanning once (at the start
+// of the marking cycle) and the root regions are all the survivor
+// regions populated during the initial-mark pause.
+class CMRootRegions VALUE_OBJ_CLASS_SPEC {
+private:
+ YoungList* _young_list;
+ ConcurrentMark* _cm;
+
+ volatile bool _scan_in_progress;
+ volatile bool _should_abort;
+ HeapRegion* volatile _next_survivor;
+
+public:
+ CMRootRegions();
+ // We actually do most of the initialization in this method.
+ void init(G1CollectedHeap* g1h, ConcurrentMark* cm);
+
+ // Reset the claiming / scanning of the root regions.
+ void prepare_for_scan();
+
+ // Forces get_next() to return NULL so that the iteration aborts early.
+ void abort() { _should_abort = true; }
+
+ // Return true if the CM thread are actively scanning root regions,
+ // false otherwise.
+ bool scan_in_progress() { return _scan_in_progress; }
+
+ // Claim the next root region to scan atomically, or return NULL if
+ // all have been claimed.
+ HeapRegion* claim_next();
+
+ // Flag that we're done with root region scanning and notify anyone
+ // who's waiting on it. If aborted is false, assume that all regions
+ // have been claimed.
+ void scan_finished();
+
+ // If CM threads are still scanning root regions, wait until they
+ // are done. Return true if we had to wait, false otherwise.
+ bool wait_until_scan_finished();
+};
+
+class ConcurrentMarkThread;
+
+class ConcurrentMark: public CHeapObj<mtGC> {
+ friend class CMMarkStack;
+ friend class ConcurrentMarkThread;
+ friend class CMTask;
+ friend class CMBitMapClosure;
+ friend class CMRemarkTask;
+ friend class CMConcurrentMarkingTask;
+ friend class G1ParNoteEndTask;
+ friend class CalcLiveObjectsClosure;
+ friend class G1CMRefProcTaskProxy;
+ friend class G1CMRefProcTaskExecutor;
+ friend class G1CMKeepAliveAndDrainClosure;
+ friend class G1CMDrainMarkingStackClosure;
+
+protected:
+ ConcurrentMarkThread* _cmThread; // The thread doing the work
+ G1CollectedHeap* _g1h; // The heap
+ uint _parallel_marking_threads; // The number of marking
+ // threads we're using
+ uint _max_parallel_marking_threads; // Max number of marking
+ // threads we'll ever use
+ double _sleep_factor; // How much we have to sleep, with
+ // respect to the work we just did, to
+ // meet the marking overhead goal
+ double _marking_task_overhead; // Marking target overhead for
+ // a single task
+
+ // Same as the two above, but for the cleanup task
+ double _cleanup_sleep_factor;
+ double _cleanup_task_overhead;
+
+ FreeRegionList _cleanup_list;
+
+ // Concurrent marking support structures
+ CMBitMap _markBitMap1;
+ CMBitMap _markBitMap2;
+ CMBitMapRO* _prevMarkBitMap; // Completed mark bitmap
+ CMBitMap* _nextMarkBitMap; // Under-construction mark bitmap
+
+ BitMap _region_bm;
+ BitMap _card_bm;
+
+ // Heap bounds
+ HeapWord* _heap_start;
+ HeapWord* _heap_end;
+
+ // Root region tracking and claiming
+ CMRootRegions _root_regions;
+
+ // For gray objects
+ CMMarkStack _markStack; // Grey objects behind global finger
+ HeapWord* volatile _finger; // The global finger, region aligned,
+ // always points to the end of the
+ // last claimed region
+
+ // Marking tasks
+ uint _max_worker_id;// Maximum worker id
+ uint _active_tasks; // Task num currently active
+ CMTask** _tasks; // Task queue array (max_worker_id len)
+ CMTaskQueueSet* _task_queues; // Task queue set
+ ParallelTaskTerminator _terminator; // For termination
+
+ // Two sync barriers that are used to synchronize tasks when an
+ // overflow occurs. The algorithm is the following. All tasks enter
+ // the first one to ensure that they have all stopped manipulating
+ // the global data structures. After they exit it, they re-initialize
+ // their data structures and task 0 re-initializes the global data
+ // structures. Then, they enter the second sync barrier. This
+ // ensure, that no task starts doing work before all data
+ // structures (local and global) have been re-initialized. When they
+ // exit it, they are free to start working again.
+ WorkGangBarrierSync _first_overflow_barrier_sync;
+ WorkGangBarrierSync _second_overflow_barrier_sync;
+
+ // This is set by any task, when an overflow on the global data
+ // structures is detected
+ volatile bool _has_overflown;
+ // True: marking is concurrent, false: we're in remark
+ volatile bool _concurrent;
+ // Set at the end of a Full GC so that marking aborts
+ volatile bool _has_aborted;
+ GCId _aborted_gc_id;
+
+ // Used when remark aborts due to an overflow to indicate that
+ // another concurrent marking phase should start
+ volatile bool _restart_for_overflow;
+
+ // This is true from the very start of concurrent marking until the
+ // point when all the tasks complete their work. It is really used
+ // to determine the points between the end of concurrent marking and
+ // time of remark.
+ volatile bool _concurrent_marking_in_progress;
+
+ // Verbose level
+ CMVerboseLevel _verbose_level;
+
+ // All of these times are in ms
+ NumberSeq _init_times;
+ NumberSeq _remark_times;
+ NumberSeq _remark_mark_times;
+ NumberSeq _remark_weak_ref_times;
+ NumberSeq _cleanup_times;
+ double _total_counting_time;
+ double _total_rs_scrub_time;
+
+ double* _accum_task_vtime; // Accumulated task vtime
+
+ FlexibleWorkGang* _parallel_workers;
+
+ ForceOverflowSettings _force_overflow_conc;
+ ForceOverflowSettings _force_overflow_stw;
+
+ void weakRefsWorkParallelPart(BoolObjectClosure* is_alive, bool purged_classes);
+ void weakRefsWork(bool clear_all_soft_refs);
+
+ void swapMarkBitMaps();
+
+ // It resets the global marking data structures, as well as the
+ // task local ones; should be called during initial mark.
+ void reset();
+
+ // Resets all the marking data structures. Called when we have to restart
+ // marking or when marking completes (via set_non_marking_state below).
+ void reset_marking_state(bool clear_overflow = true);
+
+ // We do this after we're done with marking so that the marking data
+ // structures are initialized to a sensible and predictable state.
+ void set_non_marking_state();
+
+ // Called to indicate how many threads are currently active.
+ void set_concurrency(uint active_tasks);
+
+ // It should be called to indicate which phase we're in (concurrent
+ // mark or remark) and how many threads are currently active.
+ void set_concurrency_and_phase(uint active_tasks, bool concurrent);
+
+ // Prints all gathered CM-related statistics
+ void print_stats();
+
+ bool cleanup_list_is_empty() {
+ return _cleanup_list.is_empty();
+ }
+
+ // Accessor methods
+ uint parallel_marking_threads() const { return _parallel_marking_threads; }
+ uint max_parallel_marking_threads() const { return _max_parallel_marking_threads;}
+ double sleep_factor() { return _sleep_factor; }
+ double marking_task_overhead() { return _marking_task_overhead;}
+ double cleanup_sleep_factor() { return _cleanup_sleep_factor; }
+ double cleanup_task_overhead() { return _cleanup_task_overhead;}
+
+ HeapWord* finger() { return _finger; }
+ bool concurrent() { return _concurrent; }
+ uint active_tasks() { return _active_tasks; }
+ ParallelTaskTerminator* terminator() { return &_terminator; }
+
+ // It claims the next available region to be scanned by a marking
+ // task/thread. It might return NULL if the next region is empty or
+ // we have run out of regions. In the latter case, out_of_regions()
+ // determines whether we've really run out of regions or the task
+ // should call claim_region() again. This might seem a bit
+ // awkward. Originally, the code was written so that claim_region()
+ // either successfully returned with a non-empty region or there
+ // were no more regions to be claimed. The problem with this was
+ // that, in certain circumstances, it iterated over large chunks of
+ // the heap finding only empty regions and, while it was working, it
+ // was preventing the calling task to call its regular clock
+ // method. So, this way, each task will spend very little time in
+ // claim_region() and is allowed to call the regular clock method
+ // frequently.
+ HeapRegion* claim_region(uint worker_id);
+
+ // It determines whether we've run out of regions to scan. Note that
+ // the finger can point past the heap end in case the heap was expanded
+ // to satisfy an allocation without doing a GC. This is fine, because all
+ // objects in those regions will be considered live anyway because of
+ // SATB guarantees (i.e. their TAMS will be equal to bottom).
+ bool out_of_regions() { return _finger >= _heap_end; }
+
+ // Returns the task with the given id
+ CMTask* task(int id) {
+ assert(0 <= id && id < (int) _active_tasks,
+ "task id not within active bounds");
+ return _tasks[id];
+ }
+
+ // Returns the task queue with the given id
+ CMTaskQueue* task_queue(int id) {
+ assert(0 <= id && id < (int) _active_tasks,
+ "task queue id not within active bounds");
+ return (CMTaskQueue*) _task_queues->queue(id);
+ }
+
+ // Returns the task queue set
+ CMTaskQueueSet* task_queues() { return _task_queues; }
+
+ // Access / manipulation of the overflow flag which is set to
+ // indicate that the global stack has overflown
+ bool has_overflown() { return _has_overflown; }
+ void set_has_overflown() { _has_overflown = true; }
+ void clear_has_overflown() { _has_overflown = false; }
+ bool restart_for_overflow() { return _restart_for_overflow; }
+
+ // Methods to enter the two overflow sync barriers
+ void enter_first_sync_barrier(uint worker_id);
+ void enter_second_sync_barrier(uint worker_id);
+
+ ForceOverflowSettings* force_overflow_conc() {
+ return &_force_overflow_conc;
+ }
+
+ ForceOverflowSettings* force_overflow_stw() {
+ return &_force_overflow_stw;
+ }
+
+ ForceOverflowSettings* force_overflow() {
+ if (concurrent()) {
+ return force_overflow_conc();
+ } else {
+ return force_overflow_stw();
+ }
+ }
+
+ // Live Data Counting data structures...
+ // These data structures are initialized at the start of
+ // marking. They are written to while marking is active.
+ // They are aggregated during remark; the aggregated values
+ // are then used to populate the _region_bm, _card_bm, and
+ // the total live bytes, which are then subsequently updated
+ // during cleanup.
+
+ // An array of bitmaps (one bit map per task). Each bitmap
+ // is used to record the cards spanned by the live objects
+ // marked by that task/worker.
+ BitMap* _count_card_bitmaps;
+
+ // Used to record the number of marked live bytes
+ // (for each region, by worker thread).
+ size_t** _count_marked_bytes;
+
+ // Card index of the bottom of the G1 heap. Used for biasing indices into
+ // the card bitmaps.
+ intptr_t _heap_bottom_card_num;
+
+ // Set to true when initialization is complete
+ bool _completed_initialization;
+
+public:
+ // Manipulation of the global mark stack.
+ // The push and pop operations are used by tasks for transfers
+ // between task-local queues and the global mark stack, and use
+ // locking for concurrency safety.
+ bool mark_stack_push(oop* arr, int n) {
+ _markStack.par_push_arr(arr, n);
+ if (_markStack.overflow()) {
+ set_has_overflown();
+ return false;
+ }
+ return true;
+ }
+ void mark_stack_pop(oop* arr, int max, int* n) {
+ _markStack.par_pop_arr(arr, max, n);
+ }
+ size_t mark_stack_size() { return _markStack.size(); }
+ size_t partial_mark_stack_size_target() { return _markStack.maxElems()/3; }
+ bool mark_stack_overflow() { return _markStack.overflow(); }
+ bool mark_stack_empty() { return _markStack.isEmpty(); }
+
+ CMRootRegions* root_regions() { return &_root_regions; }
+
+ bool concurrent_marking_in_progress() {
+ return _concurrent_marking_in_progress;
+ }
+ void set_concurrent_marking_in_progress() {
+ _concurrent_marking_in_progress = true;
+ }
+ void clear_concurrent_marking_in_progress() {
+ _concurrent_marking_in_progress = false;
+ }
+
+ void update_accum_task_vtime(int i, double vtime) {
+ _accum_task_vtime[i] += vtime;
+ }
+
+ double all_task_accum_vtime() {
+ double ret = 0.0;
+ for (uint i = 0; i < _max_worker_id; ++i)
+ ret += _accum_task_vtime[i];
+ return ret;
+ }
+
+ // Attempts to steal an object from the task queues of other tasks
+ bool try_stealing(uint worker_id, int* hash_seed, oop& obj);
+
+ ConcurrentMark(G1CollectedHeap* g1h,
+ G1RegionToSpaceMapper* prev_bitmap_storage,
+ G1RegionToSpaceMapper* next_bitmap_storage);
+ ~ConcurrentMark();
+
+ ConcurrentMarkThread* cmThread() { return _cmThread; }
+
+ CMBitMapRO* prevMarkBitMap() const { return _prevMarkBitMap; }
+ CMBitMap* nextMarkBitMap() const { return _nextMarkBitMap; }
+
+ // Returns the number of GC threads to be used in a concurrent
+ // phase based on the number of GC threads being used in a STW
+ // phase.
+ uint scale_parallel_threads(uint n_par_threads);
+
+ // Calculates the number of GC threads to be used in a concurrent phase.
+ uint calc_parallel_marking_threads();
+
+ // The following three are interaction between CM and
+ // G1CollectedHeap
+
+ // This notifies CM that a root during initial-mark needs to be
+ // grayed. It is MT-safe. word_size is the size of the object in
+ // words. It is passed explicitly as sometimes we cannot calculate
+ // it from the given object because it might be in an inconsistent
+ // state (e.g., in to-space and being copied). So the caller is
+ // responsible for dealing with this issue (e.g., get the size from
+ // the from-space image when the to-space image might be
+ // inconsistent) and always passing the size. hr is the region that
+ // contains the object and it's passed optionally from callers who
+ // might already have it (no point in recalculating it).
+ inline void grayRoot(oop obj,
+ size_t word_size,
+ uint worker_id,
+ HeapRegion* hr = NULL);
+
+ // It iterates over the heap and for each object it comes across it
+ // will dump the contents of its reference fields, as well as
+ // liveness information for the object and its referents. The dump
+ // will be written to a file with the following name:
+ // G1PrintReachableBaseFile + "." + str.
+ // vo decides whether the prev (vo == UsePrevMarking), the next
+ // (vo == UseNextMarking) marking information, or the mark word
+ // (vo == UseMarkWord) will be used to determine the liveness of
+ // each object / referent.
+ // If all is true, all objects in the heap will be dumped, otherwise
+ // only the live ones. In the dump the following symbols / breviations
+ // are used:
+ // M : an explicitly live object (its bitmap bit is set)
+ // > : an implicitly live object (over tams)
+ // O : an object outside the G1 heap (typically: in the perm gen)
+ // NOT : a reference field whose referent is not live
+ // AND MARKED : indicates that an object is both explicitly and
+ // implicitly live (it should be one or the other, not both)
+ void print_reachable(const char* str,
+ VerifyOption vo,
+ bool all) PRODUCT_RETURN;
+
+ // Clear the next marking bitmap (will be called concurrently).
+ void clearNextBitmap();
+
+ // Return whether the next mark bitmap has no marks set. To be used for assertions
+ // only. Will not yield to pause requests.
+ bool nextMarkBitmapIsClear();
+
+ // These two do the work that needs to be done before and after the
+ // initial root checkpoint. Since this checkpoint can be done at two
+ // different points (i.e. an explicit pause or piggy-backed on a
+ // young collection), then it's nice to be able to easily share the
+ // pre/post code. It might be the case that we can put everything in
+ // the post method. TP
+ void checkpointRootsInitialPre();
+ void checkpointRootsInitialPost();
+
+ // Scan all the root regions and mark everything reachable from
+ // them.
+ void scanRootRegions();
+
+ // Scan a single root region and mark everything reachable from it.
+ void scanRootRegion(HeapRegion* hr, uint worker_id);
+
+ // Do concurrent phase of marking, to a tentative transitive closure.
+ void markFromRoots();
+
+ void checkpointRootsFinal(bool clear_all_soft_refs);
+ void checkpointRootsFinalWork();
+ void cleanup();
+ void completeCleanup();
+
+ // Mark in the previous bitmap. NB: this is usually read-only, so use
+ // this carefully!
+ inline void markPrev(oop p);
+
+ // Clears marks for all objects in the given range, for the prev or
+ // next bitmaps. NB: the previous bitmap is usually
+ // read-only, so use this carefully!
+ void clearRangePrevBitmap(MemRegion mr);
+ void clearRangeNextBitmap(MemRegion mr);
+
+ // Notify data structures that a GC has started.
+ void note_start_of_gc() {
+ _markStack.note_start_of_gc();
+ }
+
+ // Notify data structures that a GC is finished.
+ void note_end_of_gc() {
+ _markStack.note_end_of_gc();
+ }
+
+ // Verify that there are no CSet oops on the stacks (taskqueues /
+ // global mark stack) and fingers (global / per-task).
+ // If marking is not in progress, it's a no-op.
+ void verify_no_cset_oops() PRODUCT_RETURN;
+
+ bool isPrevMarked(oop p) const {
+ assert(p != NULL && p->is_oop(), "expected an oop");
+ HeapWord* addr = (HeapWord*)p;
+ assert(addr >= _prevMarkBitMap->startWord() ||
+ addr < _prevMarkBitMap->endWord(), "in a region");
+
+ return _prevMarkBitMap->isMarked(addr);
+ }
+
+ inline bool do_yield_check(uint worker_i = 0);
+
+ // Called to abort the marking cycle after a Full GC takes place.
+ void abort();
+
+ bool has_aborted() { return _has_aborted; }
+
+ const GCId& concurrent_gc_id();
+
+ // This prints the global/local fingers. It is used for debugging.
+ NOT_PRODUCT(void print_finger();)
+
+ void print_summary_info();
+
+ void print_worker_threads_on(outputStream* st) const;
+
+ void print_on_error(outputStream* st) const;
+
+ // The following indicate whether a given verbose level has been
+ // set. Notice that anything above stats is conditional to
+ // _MARKING_VERBOSE_ having been set to 1
+ bool verbose_stats() {
+ return _verbose_level >= stats_verbose;
+ }
+ bool verbose_low() {
+ return _MARKING_VERBOSE_ && _verbose_level >= low_verbose;
+ }
+ bool verbose_medium() {
+ return _MARKING_VERBOSE_ && _verbose_level >= medium_verbose;
+ }
+ bool verbose_high() {
+ return _MARKING_VERBOSE_ && _verbose_level >= high_verbose;
+ }
+
+ // Liveness counting
+
+ // Utility routine to set an exclusive range of cards on the given
+ // card liveness bitmap
+ inline void set_card_bitmap_range(BitMap* card_bm,
+ BitMap::idx_t start_idx,
+ BitMap::idx_t end_idx,
+ bool is_par);
+
+ // Returns the card number of the bottom of the G1 heap.
+ // Used in biasing indices into accounting card bitmaps.
+ intptr_t heap_bottom_card_num() const {
+ return _heap_bottom_card_num;
+ }
+
+ // Returns the card bitmap for a given task or worker id.
+ BitMap* count_card_bitmap_for(uint worker_id) {
+ assert(worker_id < _max_worker_id, "oob");
+ assert(_count_card_bitmaps != NULL, "uninitialized");
+ BitMap* task_card_bm = &_count_card_bitmaps[worker_id];
+ assert(task_card_bm->size() == _card_bm.size(), "size mismatch");
+ return task_card_bm;
+ }
+
+ // Returns the array containing the marked bytes for each region,
+ // for the given worker or task id.
+ size_t* count_marked_bytes_array_for(uint worker_id) {
+ assert(worker_id < _max_worker_id, "oob");
+ assert(_count_marked_bytes != NULL, "uninitialized");
+ size_t* marked_bytes_array = _count_marked_bytes[worker_id];
+ assert(marked_bytes_array != NULL, "uninitialized");
+ return marked_bytes_array;
+ }
+
+ // Returns the index in the liveness accounting card table bitmap
+ // for the given address
+ inline BitMap::idx_t card_bitmap_index_for(HeapWord* addr);
+
+ // Counts the size of the given memory region in the the given
+ // marked_bytes array slot for the given HeapRegion.
+ // Sets the bits in the given card bitmap that are associated with the
+ // cards that are spanned by the memory region.
+ inline void count_region(MemRegion mr,
+ HeapRegion* hr,
+ size_t* marked_bytes_array,
+ BitMap* task_card_bm);
+
+ // Counts the given memory region in the task/worker counting
+ // data structures for the given worker id.
+ inline void count_region(MemRegion mr, HeapRegion* hr, uint worker_id);
+
+ // Counts the given object in the given task/worker counting
+ // data structures.
+ inline void count_object(oop obj,
+ HeapRegion* hr,
+ size_t* marked_bytes_array,
+ BitMap* task_card_bm);
+
+ // Attempts to mark the given object and, if successful, counts
+ // the object in the given task/worker counting structures.
+ inline bool par_mark_and_count(oop obj,
+ HeapRegion* hr,
+ size_t* marked_bytes_array,
+ BitMap* task_card_bm);
+
+ // Attempts to mark the given object and, if successful, counts
+ // the object in the task/worker counting structures for the
+ // given worker id.
+ inline bool par_mark_and_count(oop obj,
+ size_t word_size,
+ HeapRegion* hr,
+ uint worker_id);
+
+ // Returns true if initialization was successfully completed.
+ bool completed_initialization() const {
+ return _completed_initialization;
+ }
+
+protected:
+ // Clear all the per-task bitmaps and arrays used to store the
+ // counting data.
+ void clear_all_count_data();
+
+ // Aggregates the counting data for each worker/task
+ // that was constructed while marking. Also sets
+ // the amount of marked bytes for each region and
+ // the top at concurrent mark count.
+ void aggregate_count_data();
+
+ // Verification routine
+ void verify_count_data();
+};
+
+// A class representing a marking task.
+class CMTask : public TerminatorTerminator {
+private:
+ enum PrivateConstants {
+ // the regular clock call is called once the scanned words reaches
+ // this limit
+ words_scanned_period = 12*1024,
+ // the regular clock call is called once the number of visited
+ // references reaches this limit
+ refs_reached_period = 384,
+ // initial value for the hash seed, used in the work stealing code
+ init_hash_seed = 17,
+ // how many entries will be transferred between global stack and
+ // local queues
+ global_stack_transfer_size = 16
+ };
+
+ uint _worker_id;
+ G1CollectedHeap* _g1h;
+ ConcurrentMark* _cm;
+ CMBitMap* _nextMarkBitMap;
+ // the task queue of this task
+ CMTaskQueue* _task_queue;
+private:
+ // the task queue set---needed for stealing
+ CMTaskQueueSet* _task_queues;
+ // indicates whether the task has been claimed---this is only for
+ // debugging purposes
+ bool _claimed;
+
+ // number of calls to this task
+ int _calls;
+
+ // when the virtual timer reaches this time, the marking step should
+ // exit
+ double _time_target_ms;
+ // the start time of the current marking step
+ double _start_time_ms;
+
+ // the oop closure used for iterations over oops
+ G1CMOopClosure* _cm_oop_closure;
+
+ // the region this task is scanning, NULL if we're not scanning any
+ HeapRegion* _curr_region;
+ // the local finger of this task, NULL if we're not scanning a region
+ HeapWord* _finger;
+ // limit of the region this task is scanning, NULL if we're not scanning one
+ HeapWord* _region_limit;
+
+ // the number of words this task has scanned
+ size_t _words_scanned;
+ // When _words_scanned reaches this limit, the regular clock is
+ // called. Notice that this might be decreased under certain
+ // circumstances (i.e. when we believe that we did an expensive
+ // operation).
+ size_t _words_scanned_limit;
+ // the initial value of _words_scanned_limit (i.e. what it was
+ // before it was decreased).
+ size_t _real_words_scanned_limit;
+
+ // the number of references this task has visited
+ size_t _refs_reached;
+ // When _refs_reached reaches this limit, the regular clock is
+ // called. Notice this this might be decreased under certain
+ // circumstances (i.e. when we believe that we did an expensive
+ // operation).
+ size_t _refs_reached_limit;
+ // the initial value of _refs_reached_limit (i.e. what it was before
+ // it was decreased).
+ size_t _real_refs_reached_limit;
+
+ // used by the work stealing stuff
+ int _hash_seed;
+ // if this is true, then the task has aborted for some reason
+ bool _has_aborted;
+ // set when the task aborts because it has met its time quota
+ bool _has_timed_out;
+ // true when we're draining SATB buffers; this avoids the task
+ // aborting due to SATB buffers being available (as we're already
+ // dealing with them)
+ bool _draining_satb_buffers;
+
+ // number sequence of past step times
+ NumberSeq _step_times_ms;
+ // elapsed time of this task
+ double _elapsed_time_ms;
+ // termination time of this task
+ double _termination_time_ms;
+ // when this task got into the termination protocol
+ double _termination_start_time_ms;
+
+ // true when the task is during a concurrent phase, false when it is
+ // in the remark phase (so, in the latter case, we do not have to
+ // check all the things that we have to check during the concurrent
+ // phase, i.e. SATB buffer availability...)
+ bool _concurrent;
+
+ TruncatedSeq _marking_step_diffs_ms;
+
+ // Counting data structures. Embedding the task's marked_bytes_array
+ // and card bitmap into the actual task saves having to go through
+ // the ConcurrentMark object.
+ size_t* _marked_bytes_array;
+ BitMap* _card_bm;
+
+ // LOTS of statistics related with this task
+#if _MARKING_STATS_
+ NumberSeq _all_clock_intervals_ms;
+ double _interval_start_time_ms;
+
+ size_t _aborted;
+ size_t _aborted_overflow;
+ size_t _aborted_cm_aborted;
+ size_t _aborted_yield;
+ size_t _aborted_timed_out;
+ size_t _aborted_satb;
+ size_t _aborted_termination;
+
+ size_t _steal_attempts;
+ size_t _steals;
+
+ size_t _clock_due_to_marking;
+ size_t _clock_due_to_scanning;
+
+ size_t _local_pushes;
+ size_t _local_pops;
+ size_t _local_max_size;
+ size_t _objs_scanned;
+
+ size_t _global_pushes;
+ size_t _global_pops;
+ size_t _global_max_size;
+
+ size_t _global_transfers_to;
+ size_t _global_transfers_from;
+
+ size_t _regions_claimed;
+ size_t _objs_found_on_bitmap;
+
+ size_t _satb_buffers_processed;
+#endif // _MARKING_STATS_
+
+ // it updates the local fields after this task has claimed
+ // a new region to scan
+ void setup_for_region(HeapRegion* hr);
+ // it brings up-to-date the limit of the region
+ void update_region_limit();
+
+ // called when either the words scanned or the refs visited limit
+ // has been reached
+ void reached_limit();
+ // recalculates the words scanned and refs visited limits
+ void recalculate_limits();
+ // decreases the words scanned and refs visited limits when we reach
+ // an expensive operation
+ void decrease_limits();
+ // it checks whether the words scanned or refs visited reached their
+ // respective limit and calls reached_limit() if they have
+ void check_limits() {
+ if (_words_scanned >= _words_scanned_limit ||
+ _refs_reached >= _refs_reached_limit) {
+ reached_limit();
+ }
+ }
+ // this is supposed to be called regularly during a marking step as
+ // it checks a bunch of conditions that might cause the marking step
+ // to abort
+ void regular_clock_call();
+ bool concurrent() { return _concurrent; }
+
+ // Test whether obj might have already been passed over by the
+ // mark bitmap scan, and so needs to be pushed onto the mark stack.
+ bool is_below_finger(oop obj, HeapWord* global_finger) const;
+
+ template<bool scan> void process_grey_object(oop obj);
+
+public:
+ // It resets the task; it should be called right at the beginning of
+ // a marking phase.
+ void reset(CMBitMap* _nextMarkBitMap);
+ // it clears all the fields that correspond to a claimed region.
+ void clear_region_fields();
+
+ void set_concurrent(bool concurrent) { _concurrent = concurrent; }
+
+ // The main method of this class which performs a marking step
+ // trying not to exceed the given duration. However, it might exit
+ // prematurely, according to some conditions (i.e. SATB buffers are
+ // available for processing).
+ void do_marking_step(double target_ms,
+ bool do_termination,
+ bool is_serial);
+
+ // These two calls start and stop the timer
+ void record_start_time() {
+ _elapsed_time_ms = os::elapsedTime() * 1000.0;
+ }
+ void record_end_time() {
+ _elapsed_time_ms = os::elapsedTime() * 1000.0 - _elapsed_time_ms;
+ }
+
+ // returns the worker ID associated with this task.
+ uint worker_id() { return _worker_id; }
+
+ // From TerminatorTerminator. It determines whether this task should
+ // exit the termination protocol after it's entered it.
+ virtual bool should_exit_termination();
+
+ // Resets the local region fields after a task has finished scanning a
+ // region; or when they have become stale as a result of the region
+ // being evacuated.
+ void giveup_current_region();
+
+ HeapWord* finger() { return _finger; }
+
+ bool has_aborted() { return _has_aborted; }
+ void set_has_aborted() { _has_aborted = true; }
+ void clear_has_aborted() { _has_aborted = false; }
+ bool has_timed_out() { return _has_timed_out; }
+ bool claimed() { return _claimed; }
+
+ void set_cm_oop_closure(G1CMOopClosure* cm_oop_closure);
+
+ // Increment the number of references this task has visited.
+ void increment_refs_reached() { ++_refs_reached; }
+
+ // Grey the object by marking it. If not already marked, push it on
+ // the local queue if below the finger.
+ // Precondition: obj is in region.
+ // Precondition: obj is below region's NTAMS.
+ inline void make_reference_grey(oop obj, HeapRegion* region);
+
+ // Grey the object (by calling make_grey_reference) if required,
+ // e.g. obj is below its containing region's NTAMS.
+ // Precondition: obj is a valid heap object.
+ inline void deal_with_reference(oop obj);
+
+ // It scans an object and visits its children.
+ void scan_object(oop obj) { process_grey_object<true>(obj); }
+
+ // It pushes an object on the local queue.
+ inline void push(oop obj);
+
+ // These two move entries to/from the global stack.
+ void move_entries_to_global_stack();
+ void get_entries_from_global_stack();
+
+ // It pops and scans objects from the local queue. If partially is
+ // true, then it stops when the queue size is of a given limit. If
+ // partially is false, then it stops when the queue is empty.
+ void drain_local_queue(bool partially);
+ // It moves entries from the global stack to the local queue and
+ // drains the local queue. If partially is true, then it stops when
+ // both the global stack and the local queue reach a given size. If
+ // partially if false, it tries to empty them totally.
+ void drain_global_stack(bool partially);
+ // It keeps picking SATB buffers and processing them until no SATB
+ // buffers are available.
+ void drain_satb_buffers();
+
+ // moves the local finger to a new location
+ inline void move_finger_to(HeapWord* new_finger) {
+ assert(new_finger >= _finger && new_finger < _region_limit, "invariant");
+ _finger = new_finger;
+ }
+
+ CMTask(uint worker_id,
+ ConcurrentMark *cm,
+ size_t* marked_bytes,
+ BitMap* card_bm,
+ CMTaskQueue* task_queue,
+ CMTaskQueueSet* task_queues);
+
+ // it prints statistics associated with this task
+ void print_stats();
+
+#if _MARKING_STATS_
+ void increase_objs_found_on_bitmap() { ++_objs_found_on_bitmap; }
+#endif // _MARKING_STATS_
+};
+
+// Class that's used to to print out per-region liveness
+// information. It's currently used at the end of marking and also
+// after we sort the old regions at the end of the cleanup operation.
+class G1PrintRegionLivenessInfoClosure: public HeapRegionClosure {
+private:
+ outputStream* _out;
+
+ // Accumulators for these values.
+ size_t _total_used_bytes;
+ size_t _total_capacity_bytes;
+ size_t _total_prev_live_bytes;
+ size_t _total_next_live_bytes;
+
+ // These are set up when we come across a "stars humongous" region
+ // (as this is where most of this information is stored, not in the
+ // subsequent "continues humongous" regions). After that, for every
+ // region in a given humongous region series we deduce the right
+ // values for it by simply subtracting the appropriate amount from
+ // these fields. All these values should reach 0 after we've visited
+ // the last region in the series.
+ size_t _hum_used_bytes;
+ size_t _hum_capacity_bytes;
+ size_t _hum_prev_live_bytes;
+ size_t _hum_next_live_bytes;
+
+ // Accumulator for the remembered set size
+ size_t _total_remset_bytes;
+
+ // Accumulator for strong code roots memory size
+ size_t _total_strong_code_roots_bytes;
+
+ static double perc(size_t val, size_t total) {
+ if (total == 0) {
+ return 0.0;
+ } else {
+ return 100.0 * ((double) val / (double) total);
+ }
+ }
+
+ static double bytes_to_mb(size_t val) {
+ return (double) val / (double) M;
+ }
+
+ // See the .cpp file.
+ size_t get_hum_bytes(size_t* hum_bytes);
+ void get_hum_bytes(size_t* used_bytes, size_t* capacity_bytes,
+ size_t* prev_live_bytes, size_t* next_live_bytes);
+
+public:
+ // The header and footer are printed in the constructor and
+ // destructor respectively.
+ G1PrintRegionLivenessInfoClosure(outputStream* out, const char* phase_name);
+ virtual bool doHeapRegion(HeapRegion* r);
+ ~G1PrintRegionLivenessInfoClosure();
+};
+
+#endif // SHARE_VM_GC_G1_CONCURRENTMARK_HPP